X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;ds=sidebyside;f=model.cc;h=c7a71ccdb2f541869ae61bd968e78c1523c35548;hb=65a0c0d8d991b2775d15934b07cb51b422a5d20b;hp=c77d4e17d4627213d2510774fe9c5d853b91257e;hpb=def20b2249cf6902b4170965cd30a8e27ecc24f1;p=model-checker.git diff --git a/model.cc b/model.cc index c77d4e1..c7a71cc 100644 --- a/model.cc +++ b/model.cc @@ -28,6 +28,7 @@ ModelChecker::ModelChecker(struct model_params params) : obj_map(new HashTable()), obj_thrd_map(new HashTable, uintptr_t, 4 >()), promises(new std::vector()), + futurevalues(new std::vector()), lazy_sync_with_release(new HashTable, uintptr_t, 4>()), thrd_last_action(new std::vector(1)), node_stack(new NodeStack()), @@ -100,16 +101,29 @@ modelclock_t ModelChecker::get_next_seq_num() } /** - * Choose the next thread in the replay sequence. + * @brief Choose the next thread to execute. * - * If the replay sequence has reached the 'diverge' point, returns a thread - * from the backtracking set. Otherwise, simply returns the next thread in the - * sequence that is being replayed. + * This function chooses the next thread that should execute. It can force the + * adjacency of read/write portions of a RMW action, force THREAD_CREATE to be + * followed by a THREAD_START, or it can enforce execution replay/backtracking. + * The model-checker may have no preference regarding the next thread (i.e., + * when exploring a new execution ordering), in which case this will return + * NULL. + * @param curr The current ModelAction. This action might guide the choice of + * next thread. + * @return The next thread to run. If the model-checker has no preference, NULL. */ -Thread * ModelChecker::get_next_replay_thread() +Thread * ModelChecker::get_next_thread(ModelAction *curr) { thread_id_t tid; + /* Do not split atomic actions. */ + if (curr->is_rmwr()) + return thread_current(); + /* The THREAD_CREATE action points to the created Thread */ + else if (curr->get_type() == THREAD_CREATE) + return (Thread *)curr->get_location(); + /* Have we completed exploring the preselected path? */ if (diverge == NULL) return NULL; @@ -203,7 +217,7 @@ void ModelChecker::set_backtracking(ModelAction *act) { ModelAction *prev; Node *node; - Thread *t = get_thread(act->get_tid()); + Thread *t = get_thread(act); prev = get_last_conflict(act); if (prev == NULL) @@ -245,6 +259,77 @@ ModelAction * ModelChecker::get_next_backtrack() return next; } +/** + * Processes a read or rmw model action. + * @param curr is the read model action to process. + * @param second_part_of_rmw is boolean that is true is this is the second action of a rmw. + * @return True if processing this read updates the mo_graph. + */ +bool ModelChecker::process_read(ModelAction *curr, bool second_part_of_rmw) +{ + uint64_t value; + bool updated = false; + while (true) { + const ModelAction *reads_from = curr->get_node()->get_read_from(); + if (reads_from != NULL) { + mo_graph->startChanges(); + + value = reads_from->get_value(); + bool r_status = false; + + if (!second_part_of_rmw) { + check_recency(curr,false); + r_status = r_modification_order(curr, reads_from); + } + + + if (!second_part_of_rmw&&!isfeasible()&&(curr->get_node()->increment_read_from()||curr->get_node()->increment_future_value())) { + mo_graph->rollbackChanges(); + too_many_reads = false; + continue; + } + + curr->read_from(reads_from); + mo_graph->commitChanges(); + updated |= r_status; + } else if (!second_part_of_rmw) { + /* Read from future value */ + value = curr->get_node()->get_future_value(); + modelclock_t expiration = curr->get_node()->get_future_value_expiration(); + curr->read_from(NULL); + Promise *valuepromise = new Promise(curr, value, expiration); + promises->push_back(valuepromise); + } + get_thread(curr)->set_return_value(value); + return updated; + } +} + +/** + * Process a write ModelAction + * @param curr The ModelAction to process + * @return True if the mo_graph was updated or promises were resolved + */ +bool ModelChecker::process_write(ModelAction *curr) +{ + bool updated_mod_order = w_modification_order(curr); + bool updated_promises = resolve_promises(curr); + + if (promises->size() == 0) { + for (unsigned int i = 0; isize(); i++) { + struct PendingFutureValue pfv = (*futurevalues)[i]; + if (pfv.act->get_node()->add_future_value(pfv.value, pfv.expiration) && + (!priv->next_backtrack || *pfv.act > *priv->next_backtrack)) + priv->next_backtrack = pfv.act; + } + futurevalues->resize(0); + } + + mo_graph->commitChanges(); + get_thread(curr)->set_return_value(VALUE_NONE); + return updated_mod_order || updated_promises; +} + /** * This is the heart of the model checker routine. It performs model-checking * actions corresponding to a given "current action." Among other processes, it @@ -259,15 +344,16 @@ ModelAction * ModelChecker::get_next_backtrack() */ Thread * ModelChecker::check_current_action(ModelAction *curr) { - bool already_added = false; + bool second_part_of_rmw = false; ASSERT(curr); if (curr->is_rmwc() || curr->is_rmw()) { ModelAction *tmp = process_rmw(curr); - already_added = true; + second_part_of_rmw = true; delete curr; curr = tmp; + compute_promises(curr); } else { ModelAction *tmp = node_stack->explore_action(curr); if (tmp) { @@ -296,82 +382,105 @@ Thread * ModelChecker::check_current_action(ModelAction *curr) } } - /* Assign 'creation' parent */ - if (curr->get_type() == THREAD_CREATE) { + /* Thread specific actions */ + switch (curr->get_type()) { + case THREAD_CREATE: { Thread *th = (Thread *)curr->get_location(); th->set_creation(curr); - } else if (curr->get_type() == THREAD_JOIN) { - Thread *wait, *join; - wait = get_thread(curr->get_tid()); - join = (Thread *)curr->get_location(); - if (!join->is_complete()) - scheduler->wait(wait, join); - } else if (curr->get_type() == THREAD_FINISH) { - Thread *th = get_thread(curr->get_tid()); + break; + } + case THREAD_JOIN: { + Thread *waiting, *blocking; + waiting = get_thread(curr); + blocking = (Thread *)curr->get_location(); + if (!blocking->is_complete()) { + blocking->push_wait_list(curr); + scheduler->sleep(waiting); + } + break; + } + case THREAD_FINISH: { + Thread *th = get_thread(curr); while (!th->wait_list_empty()) { - Thread *wake = th->pop_wait_list(); + ModelAction *act = th->pop_wait_list(); + Thread *wake = get_thread(act); scheduler->wake(wake); } th->complete(); + break; } - - /* Deal with new thread */ - if (curr->get_type() == THREAD_START) + case THREAD_START: { check_promises(NULL, curr->get_cv()); + break; + } + default: + break; + } - /* Assign reads_from values */ - Thread *th = get_thread(curr->get_tid()); - uint64_t value = VALUE_NONE; - bool updated = false; - if (curr->is_read()) { - const ModelAction *reads_from = curr->get_node()->get_read_from(); - if (reads_from != NULL) { - value = reads_from->get_value(); - /* Assign reads_from, perform release/acquire synchronization */ - curr->read_from(reads_from); - if (r_modification_order(curr,reads_from)) + work_queue_t work_queue(1, CheckCurrWorkEntry(curr)); + + while (!work_queue.empty()) { + WorkQueueEntry work = work_queue.front(); + work_queue.pop_front(); + + switch (work.type) { + case WORK_CHECK_CURR_ACTION: { + ModelAction *act = work.action; + bool updated = false; + if (act->is_read() && process_read(act, second_part_of_rmw)) updated = true; - } else { - /* Read from future value */ - value = curr->get_node()->get_future_value(); - curr->read_from(NULL); - Promise *valuepromise = new Promise(curr, value); - promises->push_back(valuepromise); - } - } else if (curr->is_write()) { - if (w_modification_order(curr)) - updated = true; - if (resolve_promises(curr)) - updated = true; - } - if (updated) - resolve_release_sequences(curr->get_location()); + if (act->is_write() && process_write(act)) + updated = true; - th->set_return_value(value); + if (updated) + work_queue.push_back(CheckRelSeqWorkEntry(act->get_location())); + break; + } + case WORK_CHECK_RELEASE_SEQ: + resolve_release_sequences(work.location, &work_queue); + break; + case WORK_CHECK_MO_EDGES: + /** @todo Perform follow-up mo_graph checks */ + default: + ASSERT(false); + break; + } + } /* Add action to list. */ - if (!already_added) + if (!second_part_of_rmw) add_action_to_lists(curr); + check_curr_backtracking(curr); + + set_backtracking(curr); + + return get_next_thread(curr); +} + +void ModelChecker::check_curr_backtracking(ModelAction * curr) { Node *currnode = curr->get_node(); Node *parnode = currnode->get_parent(); - if (!parnode->backtrack_empty() || !currnode->read_from_empty() || - !currnode->future_value_empty() || !currnode->promise_empty()) - if (!priv->next_backtrack || *curr > *priv->next_backtrack) - priv->next_backtrack = curr; - - set_backtracking(curr); + if ((!parnode->backtrack_empty() || + !currnode->read_from_empty() || + !currnode->future_value_empty() || + !currnode->promise_empty()) + && (!priv->next_backtrack || + *curr > *priv->next_backtrack)) { + priv->next_backtrack = curr; + } +} - /* Do not split atomic actions. */ - if (curr->is_rmwr()) - return thread_current(); - /* The THREAD_CREATE action points to the created Thread */ - else if (curr->get_type() == THREAD_CREATE) - return (Thread *)curr->get_location(); - else - return get_next_replay_thread(); +bool ModelChecker::promises_expired() { + for (unsigned int promise_index = 0; promise_index < promises->size(); promise_index++) { + Promise *promise = (*promises)[promise_index]; + if (promise->get_expiration()used_sequence_numbers) { + return true; + } + } + return false; } /** @returns whether the current partial trace must be a prefix of a @@ -382,7 +491,13 @@ bool ModelChecker::isfeasibleprefix() { /** @returns whether the current partial trace is feasible. */ bool ModelChecker::isfeasible() { - return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads; + return !mo_graph->checkForRMWViolation() && isfeasibleotherthanRMW(); +} + +/** @returns whether the current partial trace is feasible other than + * multiple RMW reading from the same store. */ +bool ModelChecker::isfeasibleotherthanRMW() { + return !mo_graph->checkForCycles() && !failed_promise && !too_many_reads && !promises_expired(); } /** Returns whether the current completed trace is feasible. */ @@ -395,11 +510,109 @@ ModelAction * ModelChecker::process_rmw(ModelAction *act) { int tid = id_to_int(act->get_tid()); ModelAction *lastread = get_last_action(tid); lastread->process_rmw(act); - if (act->is_rmw()) + if (act->is_rmw() && lastread->get_reads_from()!=NULL) { mo_graph->addRMWEdge(lastread->get_reads_from(), lastread); + mo_graph->commitChanges(); + } return lastread; } +/** + * Checks whether a thread has read from the same write for too many times + * without seeing the effects of a later write. + * + * Basic idea: + * 1) there must a different write that we could read from that would satisfy the modification order, + * 2) we must have read from the same value in excess of maxreads times, and + * 3) that other write must have been in the reads_from set for maxreads times. + * + * If so, we decide that the execution is no longer feasible. + */ +void ModelChecker::check_recency(ModelAction *curr, bool already_added) { + if (params.maxreads != 0) { + if (curr->get_node()->get_read_from_size() <= 1) + return; + + //Must make sure that execution is currently feasible... We could + //accidentally clear by rolling back + if (!isfeasible()) + return; + + std::vector *thrd_lists = obj_thrd_map->get_safe_ptr(curr->get_location()); + int tid = id_to_int(curr->get_tid()); + + /* Skip checks */ + if ((int)thrd_lists->size() <= tid) + return; + + action_list_t *list = &(*thrd_lists)[tid]; + + action_list_t::reverse_iterator rit = list->rbegin(); + /* Skip past curr */ + if (already_added) { + for (; (*rit) != curr; rit++) + ; + /* go past curr now */ + rit++; + } + + action_list_t::reverse_iterator ritcopy = rit; + //See if we have enough reads from the same value + int count = 0; + for (; count < params.maxreads; rit++,count++) { + if (rit==list->rend()) + return; + ModelAction *act = *rit; + if (!act->is_read()) + return; + if (act->get_reads_from() != curr->get_reads_from()) + return; + if (act->get_node()->get_read_from_size() <= 1) + return; + } + + for (int i = 0; iget_node()->get_read_from_size(); i++) { + //Get write + const ModelAction * write = curr->get_node()->get_read_from_at(i); + //Need a different write + if (write==curr->get_reads_from()) + continue; + + /* Test to see whether this is a feasible write to read from*/ + mo_graph->startChanges(); + r_modification_order(curr, write); + bool feasiblereadfrom = isfeasible(); + mo_graph->rollbackChanges(); + + if (!feasiblereadfrom) + continue; + rit = ritcopy; + + bool feasiblewrite = true; + //new we need to see if this write works for everyone + + for (int loop = count; loop>0; loop--,rit++) { + ModelAction *act=*rit; + bool foundvalue = false; + for (int j = 0; jget_node()->get_read_from_size(); j++) { + if (act->get_node()->get_read_from_at(i)==write) { + foundvalue = true; + break; + } + } + if (!foundvalue) { + feasiblewrite = false; + break; + } + } + if (feasiblewrite) { + too_many_reads = true; + return; + } + } + } +} + /** * Updates the mo_graph with the constraints imposed from the current read. * @param curr The current action. Must be a read. @@ -423,16 +636,19 @@ bool ModelChecker::r_modification_order(ModelAction *curr, const ModelAction *rf /* Include at most one act per-thread that "happens before" curr */ if (act->happens_before(curr)) { - if (act->is_read()) { + if (act->is_write()) { + if (rf != act && act != curr) { + mo_graph->addEdge(act, rf); + added = true; + } + } else { const ModelAction *prevreadfrom = act->get_reads_from(); if (prevreadfrom != NULL && rf != prevreadfrom) { mo_graph->addEdge(prevreadfrom, rf); added = true; } - } else if (rf != act) { - mo_graph->addEdge(act, rf); - added = true; } + break; } } @@ -510,10 +726,18 @@ bool ModelChecker::w_modification_order(ModelAction *curr) /* Include at most one act per-thread that "happens before" curr */ if (act->happens_before(curr)) { - if (act->is_read()) + /* + * Note: if act is RMW, just add edge: + * act --mo--> curr + * The following edge should be handled elsewhere: + * readfrom(act) --mo--> act + */ + if (act->is_write()) { + //RMW shouldn't have an edge to themselves + if (act!=curr) + mo_graph->addEdge(act, curr); + } else if (act->is_read() && act->get_reads_from() != NULL) mo_graph->addEdge(act->get_reads_from(), curr); - else - mo_graph->addEdge(act, curr); added = true; break; } else if (act->is_read() && !act->is_synchronizing(curr) && @@ -526,9 +750,13 @@ bool ModelChecker::w_modification_order(ModelAction *curr) => that read could potentially read from our write. */ - if (act->get_node()->add_future_value(curr->get_value()) && - (!priv->next_backtrack || *act > *priv->next_backtrack)) - priv->next_backtrack = act; + if (thin_air_constraint_may_allow(curr, act)) { + if (isfeasible() || + (curr->is_rmw() && act->is_rmw() && curr->get_reads_from()==act->get_reads_from() && isfeasibleotherthanRMW())) { + struct PendingFutureValue pfv = {curr->get_value(),curr->get_seq_number()+params.maxfuturedelay,act}; + futurevalues->push_back(pfv); + } + } } } } @@ -536,6 +764,28 @@ bool ModelChecker::w_modification_order(ModelAction *curr) return added; } +/** Arbitrary reads from the future are not allowed. Section 29.3 + * part 9 places some constraints. This method checks one result of constraint + * constraint. Others require compiler support. */ + +bool ModelChecker::thin_air_constraint_may_allow(const ModelAction * writer, const ModelAction *reader) { + if (!writer->is_rmw()) + return true; + + if (!reader->is_rmw()) + return true; + + for (const ModelAction *search = writer->get_reads_from(); search != NULL; search = search->get_reads_from()) { + if (search==reader) + return false; + if (search->get_tid() == reader->get_tid() && + search->happens_before(reader)) + break; + } + + return true; +} + /** * Finds the head(s) of the release sequence(s) containing a given ModelAction. * The ModelAction under consideration is expected to be taking part in @@ -558,13 +808,15 @@ bool ModelChecker::w_modification_order(ModelAction *curr) * false otherwise */ bool ModelChecker::release_seq_head(const ModelAction *rf, - std::vector *release_heads) const + std::vector< const ModelAction *, MyAlloc > *release_heads) const { - ASSERT(rf->is_write()); if (!rf) { /* read from future: need to settle this later */ return false; /* incomplete */ } + + ASSERT(rf->is_write()); + if (rf->is_release()) release_heads->push_back(rf); if (rf->is_rmw()) { @@ -662,7 +914,7 @@ bool ModelChecker::release_seq_head(const ModelAction *rf, * @see ModelChecker::release_seq_head */ void ModelChecker::get_release_seq_heads(ModelAction *act, - std::vector *release_heads) + std::vector< const ModelAction *, MyAlloc > *release_heads) { const ModelAction *rf = act->get_reads_from(); bool complete; @@ -684,9 +936,12 @@ void ModelChecker::get_release_seq_heads(ModelAction *act, * * @param location The location/object that should be checked for release * sequence resolutions - * @return True if any updates occurred (new synchronization, new mo_graph edges) + * @param work_queue The work queue to which to add work items as they are + * generated + * @return True if any updates occurred (new synchronization, new mo_graph + * edges) */ -bool ModelChecker::resolve_release_sequences(void *location) +bool ModelChecker::resolve_release_sequences(void *location, work_queue_t *work_queue) { std::list *list; list = lazy_sync_with_release->getptr(location); @@ -698,7 +953,7 @@ bool ModelChecker::resolve_release_sequences(void *location) while (it != list->end()) { ModelAction *act = *it; const ModelAction *rf = act->get_reads_from(); - std::vector release_heads; + std::vector< const ModelAction *, MyAlloc > release_heads; bool complete; complete = release_seq_head(rf, &release_heads); for (unsigned int i = 0; i < release_heads.size(); i++) { @@ -709,14 +964,18 @@ bool ModelChecker::resolve_release_sequences(void *location) } if (updated) { + /* Re-check act for mo_graph edges */ + work_queue->push_back(MOEdgeWorkEntry(act)); + /* propagate synchronization to later actions */ action_list_t::reverse_iterator it = action_trace->rbegin(); while ((*it) != act) { ModelAction *propagate = *it; - if (act->happens_before(propagate)) - /** @todo new mo_graph edges along with - * this synchronization? */ + if (act->happens_before(propagate)) { propagate->synchronize_with(act); + /* Re-check 'propagate' for mo_graph edges */ + work_queue->push_back(MOEdgeWorkEntry(propagate)); + } } } if (complete) { @@ -810,11 +1069,15 @@ ClockVector * ModelChecker::get_cv(thread_id_t tid) bool ModelChecker::resolve_promises(ModelAction *write) { bool resolved = false; + for (unsigned int i = 0, promise_index = 0; promise_index < promises->size(); i++) { Promise *promise = (*promises)[promise_index]; if (write->get_node()->get_promise(i)) { ModelAction *read = promise->get_action(); read->read_from(write); + if (read->is_rmw()) { + mo_graph->addRMWEdge(write, read); + } r_modification_order(read, write); post_r_modification_order(read, write); promises->erase(promises->begin() + promise_index); @@ -822,7 +1085,6 @@ bool ModelChecker::resolve_promises(ModelAction *write) } else promise_index++; } - return resolved; } @@ -905,7 +1167,7 @@ void ModelChecker::build_reads_from_past(ModelAction *curr) continue; /* Don't consider more than one seq_cst write if we are a seq_cst read. */ - if (!act->is_seqcst() || !curr->is_seqcst() || act == last_seq_cst) { + if (!curr->is_seqcst()|| (!act->is_seqcst() && (last_seq_cst==NULL||!act->happens_before(last_seq_cst))) || act == last_seq_cst) { DEBUG("Adding action to may_read_from:\n"); if (DBG_ENABLED()) { act->print(); @@ -1012,6 +1274,7 @@ bool ModelChecker::take_step() { if (curr) { if (curr->get_state() == THREAD_READY) { ASSERT(priv->current_action); + priv->nextThread = check_current_action(priv->current_action); priv->current_action = NULL; if (!curr->is_blocked() && !curr->is_complete())